The purpose of this study is to demonstrate that Stractan separated young blood cells can be transfused into autologous non-human primate donors and that these cells have an improved survival compared to whole blood. Preliminary studies have shown that young red cells from rabbits can be isolated and transfused by this method. These cells demonstrate a markedly improved survival compared to unfractionated whole blood. The rhesus monkey model has been developed and demonstrates that young red cells can be isolated by this method and have improved post transfusion survival. A solid phase radioimmunoassay was developed to look for antigalactan antibodies in treated animals and in untreated normal human subjects of all ages. The eventual goal of this project will be to explore the use of this system for human transfusion, thus reducing the transfused iron load in patients with chronic anemias. The study has been expanded to use presently available cell separates to prepare units for transfusion of young red blood cells. Estimated cell ages have been derived by use of age dependent enzymes and reticulocyte counts.